In such methods, the desired assist pressure (PSdesired) can either be preset and set by the operating staff or it can be automatically determined by an expert system implemented in a control unit according to preset dependencies on certain measured values. One example is sold under the name Smartcare® system of Dräger Medical AG & Co. KG, in which a value is supplied for the desired assist pressure PSdesired on the basis of measured values of the ventilation or breathing rate, tidal volume and end-tidal CO2 concentration according to preset and preprogrammed rules and algorithms.
Besides, proportionally assisting methods are known, in which the patient's spontaneous ventilation or breathing is assisted. The degree of assist can be set separately according to the resistive and elastic components. These methods are also known under the terms “proportional assist ventilation” (PAV) and “proportional pressure assist” (PPS). The volume flow (Flow(t)) and the tidal volume (V(t)) are detected in these methods. The degree of assist is then determined with coefficients VA (Volume Assist) and FA (Flow Assist), which are to be set by the user, from the above-mentioned two measured values by the entire assist pressure being calculated as VA·V(t)+FA·Flow(t). In the prior-art respirators, which operate according to this principle of proportional pressure assist, the coefficients for the support FA and VA must be entered by the operating staff separately (cf., e.g., Younes, M.: “Proportional Assist Ventilation” in: Tobin M. J., ed. “Principles and practice of mechanical ventilation,” New York, McGraw-Hill, 1994, pages 349-369).